LT1 Backfiring???

[Ninjatech]

I recently got a 1993 Z28 with about 107,000 miles and ever since i have gotten it when i go to start it up every morning it backfires alot for the first few miles, especialy when i shift. I know weather will affect things like this sometimes but it does it in almost any temperature from freezing to almost 90. After it has been run for a while it will usualy stop backfiring and run fine. Im not sure if this has anything to do with it but it is running a aftermarket borla cat-back system also. Earlier today it started running like crap, at low RPM's (1500-2200) if i hit the gas it would start backfiring A LOT and it would have no power at all. In higher RPM's it would do better, not as well as it normaly runs but it would be smoother. If anyone has any ideas at all let me know. I have this gut feeling that it is going to need a rebuild soon... If it does i would like to build it up as a 383 stroker. Has anyone ever had experience with an LT1 stroker? Or would i be better off rebuilding as a 350?

Thanks

[HotRoder]

Your most likely talking about getting new pistons and connecting rods for more of a stroke and more intake which kicks ass!! Do it!!! uh you said that the car has some mods right so mabey its the camshaft causing the backfireing. If some dude put an aftermarket one in with bad timing everything would suck bad and you would get alot of backfireing. if the exhaust valve is slightly open during compression(power stroke or explosion in the combustion chamber) this can cause a backfire. there is a time at high rpms called valve overlap which means bolth valves stay open for a little bit during the exhaust stroke and its normal. in some situations this can actualy cause fire to come out the exhaust. When you start you car up in the morning tell me do you have a blueish or whiteish tinge of smoke comming out? if you do you may have some other problems to deal with like interior oil and collant leaks.
Make sure the car doesnt overheat too cause those engines run real hot.

[grnhrnt]

Opti-Spark, that is prolly the reason. 93-95.5 they had that as the 'distributor, or coil pack' it was something that they got rid of and if i were you i would either convert to the 96+ coil pack, or get that opti-spark advantage or something. But yea.

[Murco]

Replace your distributor cap and rotor (one unit), it should solve your problem. The 93-94 Z's collected moisture in the "distributor cap" and later ones, as well as aftermarket replacements, have a modified drip hole to drain them. The distributor unit will be about $100.00, and consider some good MSD wires while your under there!

[DirtyDan]

Originally posted by grnhrnt
Opti-Spark, that is prolly the reason. 93-95.5 they had that as the 'distributor, or coil pack' it was something that they got rid of and if i were you i would either convert to the 96+ coil pack, or get that opti-spark advantage or something. But yea.

93-94 Camaros had an Unvented Opti Spark, 95-97 Camaros had a vented optispark. Both are very prone to damage by moisture. And the coil packs were not offered on a LT1 motor but they can be added on with a LTCC module but you still need to use the opti for the high/low resolution pulses for the computer. The coil pack ignition came out on the LS1 motors in 1998 with the Gen 3 smallblock. Have you checked your motors compression yet? The miss could be caused by blowby, leaking valves, damaged opti, etc, etc. Just a little hint though check your wires and coil first . I'm in the process of doing a 396 stroker right now you will need around 8,000.00 to do a good stroker with heads, intake, crank, rods, pistons, rings, block work & clearancing, splayed caps, gaskets, tuning, and other things.

[94Z_Camaro]

yea dude i know what you mean. mine does it too. i have no performance mods (execpt a k&n air filter). it doesnt really do the classic loud back fire but it kinda just sputters its kinda hard to explain.